Subsurface tunnels can be used for illicit activities such as cross-border smuggling of people, weapons and/or drugs, and therefore there is an ongoing need for methods and apparatus for cost-effective techniques for accurately detecting locations and other parameters of subsurface tunnels, preferably in real-time or near real-time. It may be important to detect not only the presence and location of tunnels but also temporal changes in their dimensions. Towards this end, it might be useful to detect subsurface tunnels from a detection device at a variety of locations rather than from a single location.
Pipeline pigs are known in the art for separating between different fluids flowing through a pipeline, for internal cleaning of pipelines, and for inspection of the physical condition of the pipeline itself (e.g., for detecting cracks and leaks). Embodiments of the present invention disclose the adaptation of a pipeline pig tool for detecting subsurface tunnels, and methods and system for its use.